Class ShardStrategy<T extends Endpoint>

java.lang.Object

services.moleculer.strategy.Strategy<T>

services.moleculer.strategy.ArrayBasedStrategy<T>

services.moleculer.strategy.XorShiftRandomStrategy<T>

services.moleculer.strategy.ShardStrategy<T>

public class ShardStrategy<T extends Endpoint>
extends XorShiftRandomStrategy<T>

Sharding invocation strategy. Using consistent-hashing.
More info: https://www.toptal.com/big-data/consistent-hashing

See Also:

• RoundRobinStrategy
• NanoSecRandomStrategy
• XorShiftRandomStrategy
• SecureRandomStrategy
• CpuUsageStrategy
• NetworkLatencyStrategy

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	ShardStrategy.Ring

Field Summary

Fields

Modifier and Type	Field	Description
protected final int	cacheSize	Size of the memory cache (0 = disabled)
protected final Function<String,Long>	hash	Hasher function (generated hash is 32 bits long, default method is MD5)
protected final AtomicReference<ShardStrategy.Ring>	ringRef	The "hash ring" (https://www.toptal.com/big-data/consistent-hashing)
protected final Integer	ringSize	Ring size (optional)
protected final String	shardKey	Shard key's path (eg.
protected final boolean	useMeta	Size of the memory cache (0 = disabled)
protected final int	vnodes	Number of virtual nodes

Fields inherited from class XorShiftRandomStrategy

rnd

Fields inherited from class ArrayBasedStrategy

endpointCache, endpoints, nodeID, preferLocal

Constructor Summary

Constructors

Constructor	Description
ShardStrategy(ServiceBroker broker, boolean preferLocal, String shardKey, int vnodes, Integer ringSize, int cacheSize, Function<String,Long> hash)

Method Summary

Modifier and Type	Method	Description
void	addEndpoint(T endpoint)
protected String	getKeyFromContext(Context ctx)
Endpoint	next(Context ctx, Endpoint[] array)
protected void	rebuild()
boolean	remove(String nodeID)

Methods inherited from class ArrayBasedStrategy

getAllEndpoints, getEndpoint, getEndpointsByNodeID, isEmpty

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

shardKey

protected final String shardKey

Shard key's path (eg. "userID", "user.email", etc.)

vnodes

protected final int vnodes

Number of virtual nodes

ringSize

protected final Integer ringSize

Ring size (optional)

useMeta

protected final boolean useMeta

Size of the memory cache (0 = disabled)

cacheSize

protected final int cacheSize

Size of the memory cache (0 = disabled)

ringRef

protected final AtomicReference<ShardStrategy.Ring> ringRef

The "hash ring" (https://www.toptal.com/big-data/consistent-hashing)

hash

protected final Function<String,Long> hash

Hasher function (generated hash is 32 bits long, default method is MD5)

Constructor Details

ShardStrategy

public ShardStrategy(ServiceBroker broker,
 boolean preferLocal,
 String shardKey,
 int vnodes,
 Integer ringSize,
 int cacheSize,
 Function<String,Long> hash)

Method Details

addEndpoint

public void addEndpoint(T endpoint)

Overrides:

addEndpoint in class ArrayBasedStrategy<T extends Endpoint>

remove

public boolean remove(String nodeID)

Overrides:

remove in class ArrayBasedStrategy<T extends Endpoint>

next

public Endpoint next(Context ctx,
 Endpoint[] array)

Overrides:

next in class XorShiftRandomStrategy<T extends Endpoint>

getKeyFromContext

protected String getKeyFromContext(Context ctx)

rebuild

protected void rebuild()